Due to their excellent stretch characteristics, elastic fibers are widely used in industrial materials applications and stretch apparel applications such as legwear, underwear and sportswear.
Among such elastic fibers, polyurethane elastic fibers have been used in a particularly wide diversity of applications, but polyurethane elastic yarn has the drawbacks that it is easily degraded and discolored by light. For this reason, when stretch fabric products are displayed in stores, worn as clothing or washed and then dried outdoors and so forth, the polyurethane elastic yarn that was used gradually becomes brittle due to light.
Incidentally, to prevent the polyurethane elastic yarn from becoming brittle due to light, there is known art for producing polyurethane elastic fiber by spinning a spinning starting solution containing polyurethane supplemented with various ultraviolet light absorbents (Patent References 1, 2). Furthermore, there is known art for copolymerizing specified ultraviolet light absorbents with polyurethane in order to maintain excellent resistance to light and to prevent loss of the ultraviolet light absorbents due to abrasion, heat treatment and dying in the high-level processing steps or due to washing and dry cleaning after being made into a fabric product (Patent Reference 3).
These techniques, however, all have the objective of preventing degradation by light, and due to the addition of ultraviolet light absorbents, the fracture strength and elongation characteristics and recovery characteristics of the polyurethane elastic yarn immediately after spinning end up being the same as or, depending on the case, worse than those of polyurethane elastic yarn in which no ultraviolet light absorbents were added.